The present invention is directed to an automatic wafer processing system and method therefor and more specifically to a system for automatically handling and treating silicon wafers used in the production of integrated circuits.
Automatic wafer processing systems are well-known in the art as shown by Lasch U.S. Pat. No. 3,645,581, entitled "Apparatus and Method For Handling and Treating Articles." Here air bearings are used to transfer articles from a wafer supply storage unit to a coating unit which coats the wafer with material such as photoresist and then over another air bearing transfers the wafer to receive storage unit. A detailed explanation of at least one type of air bearing is given in another Lasch U.S. Pat. No. 3,718,371, entitled "Fluid Bearing Track Structure and Components Thereof" which illustrates both curved and straight air bearing tracks some of which are bidirectional. More sophisticated air bearing track structures or one of a different type at least is illustrated in Flint U.S. Pat. No. 3,747,753 entitled "Fluid Bearing Apparatus and Method for Handling and Gaging Articles." Sorting is accomplished by selectively diverting wafers to several wafer receive storage units. In the Flint '753 patent the cited references also show many types of track unit intersections although not of the air bearing type. A second Flint U.S. Pat. No. 3,948,564 entitled "Fluid Bearing Apparatus and Method Utilizing Selective Turn Table Diverter Structure" shows a wafer buffer unit between two other units of the system where an air bearing type turn table is operable to either store incoming wafers or provide an exit for outgoing wafers.
Also in Lasch U.S. Pat. No. 3,930,684 entitled "Automatic Wafer Feeding and Pre-Alignment Apparatus and Method" relative to the buffer unit of the '564 Flint patent there is illustrated in FIG. 4 a relatively simple type of buffer station as explained in column 16 of the patent which is capable of temporarily retaining a single wafer.
All of the foregoing patents are assigned to the present assignee.
As integrated circuit processing technology has evolved it has required the use of many additional processing techniques for the treatment of the initial silicon wafer which is the raw material of the integrated circuit. Thus special purpose automated processing systems have been developed suitable for each type of wafer processing.